Battery charging problem

[malced]

I have a Kubota B1200DT which I believe is a grey import since all the decals on it are in Japanese.
The charging light suddenly came on while it was running and sure enough a test proved that the battery was no longer being charged.
I have tested the alternator (permanent magnet type) and it is putting out about 18 volts. This tractor has separate rectifier and regulator units. The rectifier diodes appear to be ok so I suspect that the fault is in the regulator. The regulator is a solid state one but has no identifying marks on it. Does anyone have any information about it or know if it is possible to test this regulator without special equipment please?

 

[davesl708]

Have you tested the battery?
You can test the regulator to determine its output. A multi-meter will do all the test you need.

 

[100 td]

One of these maybe?
Amazon.com: Holdwell Voltage Regulator for Kubota Tractor B7100D B7100HST-D B7100HSTE 12V: Automotive

 

[malced]

Thank you for your replies. I have stripped back the covering on the wiring loom and found some broken wires which I reconnected. I started the engine and the charging light went out so I thought I had cured the problem. No such luck! I stopped the engine and when I turned the key to start it again the charge light flashed briefly then went out. The battery is still not being charged. Every time I switch on now the same thing happens, the charge light flashes and goes out before the engine is started and there is no charge getting to the battery. Has anyone come across this problem? Any suggestions as to what might be the cause of this fault please?

 

[100 td]

I have tested the alternator (permanent magnet type) and it is putting out about 18 volts. This tractor has separate rectifier and regulator units. The rectifier diodes appear to be ok so I suspect that the fault is in the regulator.

One of these maybe?
Amazon.com: Holdwell Voltage Regulator for Kubota Tractor B7100D B7100HST-D B7100HSTE 12V: Automotive

The battery is still not being charged. Every time I switch on now the same thing happens, the charge light flashes and goes out before the engine is started and there is no charge getting to the battery. Has anyone come across this problem? Any suggestions as to what might be the cause of this fault please?

A dynamo puts out AC, a rectifier changes to DC, a regulator controls the output voltage in DC. Do you have 18v AC or DC? Where is this measured? What are you chasing?

 

[malced]

An update. The alternator on my tractor is a 3 phase, and having scoured the internet I have not found any references to any other Kubota tractor having the same type of alternator or wiring arrangement to mine. It incorporates the water connection to the top of the radiator similar to the B7100 but as far as I can tell all the other permanent magnet alternators are single phase. Having no wiring schematic I have had to draw my own and it seems that the idea of the 3 phases is to increase the alternator output to compensate for when the lights are switched on. I have removed the alternator from the tractor and bench tested it. The results I got were 10v, 4v and 2v from each of the phases respectively so the alternator has definitely failed. I only tested 1 phase originally and it seems that it has gone rapidly downhill since then!
The problem I am having at the moment is with the dealer I bought my tractor from. He is situated about 400km from where I live, but as my tractor is still under guarantee for parts going local is not an option. I have been talking to him but he insists that the alternator is a dc dynamo and that it must be the regulator at fault! So the stage I am at is that he is going to send me a new regulator.
I will humour him and fit it but I know what the result will be. I get the feeling that to source a replacement alternator for me is going to be difficult and expensive and he really wants to avoid it if possible.

 

[CCWKen]

Can you post a picture of this "alternator/dynamo"? Also include a picture of the "separate rectifier and regulator units". This is nothing like what I've seen from Kubota. I wonder if the engine is even Kubota.

 

[100 td]

How many wires entering/leaving the dynamo in total?
Colours? Possibly White, Yellow & Brown?
Possibly White/Green, Blue & White/(Black or Brown)? plus possibly 2 reds of slightly different size?
How many coils in the dynamo, 3, 6, 8 or other?
How many LARGE diodes in the main rectifier circuit?
And this is definitely a permanent magnet generator, ie., no brushes and no excitation winding?
When bench testing, ensure you spin the dynamo at 4000 rpm, measure each lead to case(ground), as well as each lead to each other, and document the results.
Having no first hand experience with these dynamos, I say the following with caution. Dynamos generally are very robust, as they are limited by the permanent magnet power, ie., they can not be over excited etc., so the windings should hold up very well and should be able to handle a short circuit. So it will be interesting to find out if the coils have failed at all.

 

[100 td]

I doubt it is a 3 phase PMG, if it has an extra leg for light wiring, it may have separate coils which it switches into circuit to supply the lamps.
EDIT: I reckon I found a similar circuit to yours, which appears to switch in extra capacity (I expect extra coils), when the light switch is turned on.

 

[CCWKen]

There's no extra coils in your diagram. It's set up to run the lights on AC and charge the battery with DC. It the lights aren't on, there's no flow of AC. Many older lawn tractors do the same thing using a 2 (sometimes 3) segment alternator, especially the Briggs engines. One wire from the coil will have an in-line diode to charge the battery and the other one/two wires are used strictly for lights. Others had a separate diode bridge, and depending on the load, used DC for lights.

The OP stated there were separate modules for the rectifier and regulator. Perhaps the regulator is used strictly for gauges or something. That's why I'd like to "see" what he has.